The present invention relates to a connector for flat cable, and more particularly, to a connector having multiple electrical contacts which are assembled to conductors of a flat cable. The invention further relates to a technique for assembling a connector to a flat cable by successively aligning and relocating wires of the cable with corresponding contacts.
Flat cable consists of a plurality of wires in a parallel array embedded in a jacket of insulation. The wires are also coplanar, giving the cable the appearance of being flat. The insulation jacket typically is extruded or built up with laminates, encasing each wire in insulation which separates the wires laterally from one another. Due to manufacturing tolerances the conductors drift from desired spacing and parallel alignment. This creates a significant problem in registration of the conductors with corresponding contacts of the connector. U.S. Pat. Nos. 3,820,055 and 3,964,816 disclose the practical method of assembling a connector onto flat cable. The connector includes slotted plate type contacts laterally spaced apart. The cable conductors are placed in registration over the contacts. Then the wires are pressed into slots of corresponding contacts. All of the wires are inserted simultaneously in the contact slots without having to handle each wire separately. This assembly method assumes that the wires are disposed correctly in the cable and thereby in alignment with the contacts for proper insertion therein. However, if a wire is misaligned in the cable jacket, as is often the occurrence because of manufacturing tolerances, it may fail to make effective electrical engagement with a contact.
Flat cable is becoming miniaturized. For example the centerline spacing of wires in a flat cable has narrowed from 0.1 inches to 0.025 inches, largely as a result of an electrical requirement for controlled impedance cable, typically in the range of 90 to 120 ohms, made possible by the availability of superior dielectrics such as polytetrafluroethylene. The wire thickness ranges from 0.006 to 0.010 inches, which means the space laterally between wires varies from 0.015 to 0.019 inches, requiring miniaturization of the contacts. Miniaturization of the contacts creates difficulty in contact fabrication and aggravates the problem of registration of the wires with the contacts prior to insertion therein. For example, each contact of U.S. Pat. No. 3,820,055 is formed from a metal plate provided with a wire receiving slot. Sufficient metal is required on both sides of the slot to resist deformation when the wire is inserted. Therefore the width of the plate remains relatively large, which prevents use of the contact with narrowly spaced apart conductors. In U.S. Pat. No. 3,964,816 the contacts of plate form disclosed therein are of cylindrical or barrel configuration. The barrel configuration is therefore difficult to miniaturize because of substantial deformation stresses required for bending in a circle. This contact has the advantage of two slots which provide two pairs of gripping jaws for connection to each wire.
U.S. Pat. No. 3,760,331, discloses a contact which has opposed U-shaped plates receiving a wire therebetween. Each end of the plates is bent in a smooth curve to form the U-shape. Each end is also provided with serrated edges which penetrate insulation on an individual wire. The contacts advantageously provide two pairs of wire gripping jaws for each inserted wire. However the metal stock thickness and the smoothly curved U-shape of the opposed plates provide a bulkiness unsuitable for use with closely spaced wires such as in a flat cable.